Electric circuits



Oct- 20, 1925; 1,557,860

R. c. MATHES ELECTRIC CIRCUITS Original Filed Jan. 15, 1920 Fig. l.

Invemor: RoberT O MaThes Patented a. 20, 1925.

.' UNITED STATES PATENT OFFICE.

ROBERT C. MATHES, OF WYOMING, JERSEY, ASSIGNOR TO WESTERN ELECTBIC 1 COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ELECTRIC crnour'rs.

Application filed January 15, 1920, Serial No. 351,805. Renewed February 20, 1924.

' T0 aZZ whom it may concern Be it known that I, ROBERT C. MATHES, a citizen of the United States, residing at Wyoming, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements. in Electric Circuits, of which the following is a full, clea'r, concise, 'and exact description; 4

This invention relates to electric circuits,

and more particularly .it rel-ates to means for reducing the distortion in a repeating system. 7 i

An embodiment of the invention in which the effective input capacity of a vacuum tube is made to serve as reactance of an end section of a filter has been chosen to illustrate the invention, the scopeof the invention, however, [being defined in the claims forming apart of this application.

-As is well known in the art, weak currents-or signalsmay be amplified to any desired degree by impr sing them on one or more vacuum tube amplifiers arranged to work into each other by suitable circuit 2 as an amplifier, it has been. found that a tube works most-efiiciently if the impedance between the control electrode and the.

cathode is composed substantially of re-- sistance with no capacity component. .In that form of the vacuum tube wherein the control electrode or grid is within the tube and adjacent the cathode there is present acertain amount of capacity between the cathode and the grid dependent in value upon the size of the electrodes and the distance therebetween. This capacity effect is found to be appreciable even for currents of-fre 'quencies as low as 2,000 cycles or less and it has been found that the presence of this capacity efiect causes a certain amount of I distortion in thecurrent waves to be repeated by the tube. capacity is to produce a falling oif in efficiency ,of thecircuit at the upper part of the frequency range to be transmitted, thereby serving as a limitation to the usefulness of thG dGVlCB." I

It has furthermore been found conven-' ient in" employing a vacuum tube as a repeater,-to have associated with the repeater,

' a wave filter for limiting the range of frequency impressed on the 'tube from the incomin line. The general type of such a filter is own, for example, in the Campbell series and in shunt with the line ofvsu'ch values as to prevent the undesired freuencies from passing therethrough, but ofering little or no resistance to the passage of frequencies-it is desired to impress on the repeater. l

The calculation of the values of the im-' 5 pedance elements for each section of such a'wave filter has hitherto been made without taking into account the capacity efi'ect existing between the input: electrodes of the amplifier. In accordance with this invention, however, the condenser em loyed 1n that section of the filter immediate y precedconnections. In" employing a vacuum tube.

The general effect of this ing the repeater is changed so that the sum of the capacity of this condenser and the capacity of the. tube is equal to the desired capacity for that seetion of the filter. This change in the capacity element of the filter serves to neutralize the internal capacity of the tube for the frequencies of the current impressed thereon, thereby improving'to a considerable degree, the transmission characteristics of the repeater.

This invention will be better understood by reference to the following detailed description taken in connection with the draw ings, in which Fig. 1 represents this invention in connection with a band wave filter and Fig.2 represents the invention in connection with an ultra wave filter.

Referring now to Fig. 1 of the drawings, 4 is a vacuum tube re eater having a cathode 5, a control electro e 6 and an anode 7, which is adapted to impress on the out-. going line 88 amplified currents originating in source 9. Located between source 9 and-tube 4 is a'wave filter of a plurality of sections, consisting of inductances'lO, 11 and 12, capacities 13, 14 and 15 in shunt to the line, andinductances 16 and 17 and capacities 18 and 19 in series with theline. 0 As described in the above mentioned Campbell patent, values may be assigned to these inductance and capacity elements such that the wave filter 'w ll readily transmit frequencies within a given ran but will supfor the shunt circuit for a full section of the wave filter. Condenser-15 should be of such a value'that, taken in connection .with the i so e'fiective capacity between the grid and -cathode of tube 4, the combination of the two capacities isequal to one-half of the proper shunt capacity of a full section of the filter.

This kind of av termination of a filter is usually called a mid-shunt termination. This mid-shunt termination is preferable since the impedance of the filter at mid-shunt approximates a pure resistance.

In case, however, it is desiredto terminate the filter. at full-shunt-section, inductance 12 should have the same value as inductance 11 and'the sum of the grid capacity and capacity 15 should be .equal to the capacity 14, By embodying the grid capacity as an element of the wave filter, the disturbing effect produced eliminated. This modification of the Wave filter will, therefore, improve to'a considerable degree, the quality of the transmission. between source 9 and the outgoing line 8.

Resistance 25 which is connected between the grid and the cathode of tube 4 should be of a value equal to the impedance of the filter at its point of connection therewith, lookingin. the direction of the line.

Fig. 2 shows this invention in connection with a wave filter of a type which transmits frequencies below adesired value while suppressing frequencies thereabove. The filter is shown as consisting of capacities 27 5 28 and 29, in shunt to the line and inductances 30 and 31 inseries with the line. The sum of the capacity of condenser '29 and the capacity between the electrodes 5 and 6 of tube 4-sl1ould be equal to the value condenser 29 normally would have in the absence of repeater 4 for giving the filter the desired The sections of filter disclosed herein are similar in the sense that" each section is made u .of like reactances, coils and condensers similarlyarranged. The corresponding re} actances in successive sections may be equal, but the use of the word similar is not intended to imply that theyare necessarily e ml, for they'may be graded along the fi ter from sectionto section. What is claimed is: H 1. In combination, awave filter and an -1u-rrical discharge device associated thereby the grid capacity is thereby with, said device having an effective internal impedance comprising a reslsta-nce component and a reactance component, said wave filter having a plurality of impedances of such values with respect to each other and to said reactance component as tov cause said filter and said device to transmit certain desired frequencies while suppressingothers, and one of said filter impedances having such a value as to effectively suppress said reactance component. Y

2. In'combination, an electrical discharge device having an internal impedance com- I prising a resistance component and a reactance component, a wave filter of a plurality of sections comprising an incoming line, each of. said sections comprising an impedance element inseries uith said line and an impedance element in shunt to said line, one of said-sections having a reactance element dependent in value on said reactance component.

3. In combination, an electrical discharge I device having an eflective internal impedance comprising "a resistance component and a "capacity component, a line, a wave filter connected to said device and said line, said wave filter comprising a plurality of.

- sections, eachlof said sections comprising impedance elements in shunt and in series with said line of such values as to trans- -mit certain frequencies ,While suppressing others, a shunt impedance in the section of said wave filter adjacent to said device havthcrefor to cause said last mentioned section to have the same electrical characteristics as the preceding section thereof 'whereby the effect of the capacity component of saiddevice may be neutralized.

4. In combination, a'line, an electrical dis charge device'having input and output 'electrodes, the impedance between said input electrodes comprising a resistance component and a capacity component, a wave filter between said line and said device comprising a Hpluralityof sections each comprlslng an impedance element in series with the line and a condenser in shunt to the line, the condenser on the last section of said wave filter having a value less than the proper value for the capacity of said section by an amount equal to the capacity between said input electrodes.

5. In combination, a source of currents. a vacuum tube for am lifying currents of certain frequencies 0 said source, .and means comprising impedance elements between said source and said tube for preventing-undesired frequencies of said source from being. impressed on said tube and for neutralizing, the capacity component being a value. 'difierent from that required I I of certain frequencies of said source, and

. means comprising impedance elements be tween said source and said tube for preventing undesired frequencies of said source from being impressed. on said tube and for substantially neutralizing a reactance' ef' feet between the electrodes of said tube.

7. In combination, an electrical discharge.

device having an effective internal imped-. .ance comprislng a resistance component and a reactance component, a line, a wave filter connected to said device and said line and comprising a plurality of sections, each of said sections comprising an impedance element in shunt to said line and an impedance element in series with said line of such values as to transmit certain frequencies while suppressing others, one of the impedances in that section of said wave filter adjacent said device having a' value difi'erent from that required therefor to cause said last mentioned section to have the same electrical characteristics as a' preceding section thereof, whereby the effect of the reactance component of said device may be substantially neutralized.

8. In combination, an electricaldischarge device comprising a plurality of electrodes,-

a line, a localized electrical, network connected to said device and said. line, said network comprising a plurality of sections, each of said sections "comprising an impedanceelement in. shunt to said .line and an impedance element in series with saidv line, one of said 'lmpedance elements in each of-a plurality of said sections having the same value, the corresponding impedance element in another of said sections "havmg a value dlfl'ering from the previous mentioned value b an amount dependent upon an internal impedance characteristic said device.

9. In combination, a transmission controlling circuit and a wave amplifying de-' vice associated therewith having an effective reactance facing said circuit, said circuit having a plurality of impedances of such values and arrangement with respect to each other and to said reactance that said circuit and said device transmit with practically uniformly negligible attenuation currents of all frequencies of a range lying hetween an upper and a lower frequency limit, while attenuating and approximate- 1y extinguishin I currents of neighboring frequencies, an one of said impedances havingsuch a value .as to effectively sup L press said reactances.

' 10. In combinatioman electricaldischarge dev ce having an internal reactance, a wave filt r associated with said device; and com--- prising impedances, said impedances being so constructed and, arranged that said 'filter transmits an extended range of fre 'uencies while suppressinganother extende range tion a predetermined band 0 I whilev substantially suppressing frequencies, lying without the band, and a translating of frequencies, and one of saidimpedances substantially suppressing frequencies lying without the band, and a translating device associated with said filter, said translating.

device being so connected to the filter that the reactance of said device functions as at least a ortion of'one of the reactanee elements oft e filter. 1

12. In a selective circuit arrangement, a

' filter comprising a plurality of similar sec-.

tions, each complete section consisting of lumped reactive series and shunt im edan'ceelements so proportioned that the lter structure will transmit with substantially equal attenuation a predetermined band of requencies of aconsiderable ,range, while substantially suppressing frequencies lying without the band, and a translating device associated with said filter, said translating device being so connected to the filter that there'actance of said device functions as one of said impedance elements of theJast sectionof the filter. I

43. Ina selective circuit arrangement, a

filter comprising a plurality of similar sec-. tions, each complete section consisting of.

lumped reactive-series and shunt impedance elements so proportioned that the filter structure will transmit with equal attenuation a predetermined band of frequencies,

while substantially sup ressing frequencies lying without the ban and a translating device associated withs'a'id filter, said translating device being so connected to the filter that the effective capacity of said device functions as a capacity element of. the filter.

14. In a selective circuit arrangement, .a filter com rising aplurality of'similar sections, eac complete section, consisting of lumped reactive series and shunt impedance elements so proportioned that the filter structure will transmit, with e ual attentuadevice associated with said filter, said transfrequencies,

lating device being so connected to the filter that the efiective capacity of said device functions asa capacity element of the last section of the filter.

filter of therecurrent section type having a critical. cut-ofi frequency, and transmit ting without substantial attenuation cur-, rents of a. considerable finite range "of frex .15. In'a selective circuit arrangement, a v

quencies on one sidethereof, and substantially attenuating currents of frequencies on the other side of said critical frequency, 1n

' combination with a translating device connected to said filterand having a reactance ,facing'said filter, said'filter having a special 1 section composed of impedance elements and each section being composed of lumped,

impedance elements, and the filter as a whole with a terminal translating device having reactance components which; are substituted, in part, at least, as the impedanceelements of t e proper end section of the filter to produce a minimum of reflection effects at the end of the filter.

In witness whereof, I hereunto subscribe my name.this 12th day of January, A. D.

1920. ROBERT 0.. MATHES. 

